/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package javax.servlet.jsp;

import javax.servlet.Servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.jsp.PageContext;

/**
 * <p>
 * The JspFactory is an abstract class that defines a number of factory methods
 * available to a JSP page at runtime for the purposes of creating instances of
 * various interfaces and classes used to support the JSP implementation.
 * <p>
 * A conformant JSP Engine implementation will, during it's initialization
 * instantiate an implementation dependent subclass of this class, and make it
 * globally available for use by JSP implementation classes by registering the
 * instance created with this class via the static
 * <code> setDefaultFactory() </code> method.
 * <p>
 * The PageContext and the JspEngineInfo classes are the only
 * implementation-dependent classes that can be created from the factory.
 * <p>
 * JspFactory objects should not be used by JSP page authors.
 */

public abstract class JspFactory {

	private static volatile JspFactory deflt = null;

	/**
	 * Sole constructor. (For invocation by subclass constructors, typically
	 * implicit.)
	 */
	public JspFactory() {
	}

	/**
	 * <p>
	 * set the default factory for this implementation. It is illegal for any
	 * principal other than the JSP Engine runtime to call this method.
	 * </p>
	 * 
	 * @param deflt
	 *            The default factory implementation
	 */

	public static void setDefaultFactory(JspFactory deflt) {
		JspFactory.deflt = deflt;
	}

	/**
	 * Returns the default factory for this implementation.
	 * 
	 * @return the default factory for this implementation
	 */

	public static JspFactory getDefaultFactory() {
		return deflt;
	}

	/**
	 * <p>
	 * obtains an instance of an implementation dependent
	 * javax.servlet.jsp.PageContext abstract class for the calling Servlet and
	 * currently pending request and response.
	 * </p>
	 * 
	 * <p>
	 * This method is typically called early in the processing of the
	 * _jspService() method of a JSP implementation class in order to obtain a
	 * PageContext object for the request being processed.
	 * </p>
	 * <p>
	 * Invoking this method shall result in the PageContext.initialize() method
	 * being invoked. The PageContext returned is properly initialized.
	 * </p>
	 * <p>
	 * All PageContext objects obtained via this method shall be released by
	 * invoking releasePageContext().
	 * </p>
	 * 
	 * @param servlet
	 *            the requesting servlet
	 * @param request
	 *            the current request pending on the servlet
	 * @param response
	 *            the current response pending on the servlet
	 * @param errorPageURL
	 *            the URL of the error page for the requesting JSP, or null
	 * @param needsSession
	 *            true if the JSP participates in a session
	 * @param buffer
	 *            size of buffer in bytes, PageContext.NO_BUFFER if no buffer,
	 *            PageContext.DEFAULT_BUFFER if implementation default.
	 * @param autoflush
	 *            should the buffer autoflush to the output stream on buffer
	 *            overflow, or throw an IOException?
	 * 
	 * @return the page context
	 * 
	 * @see javax.servlet.jsp.PageContext
	 */

	public abstract PageContext getPageContext(Servlet servlet,
			ServletRequest request, ServletResponse response,
			String errorPageURL, boolean needsSession, int buffer,
			boolean autoflush);

	/**
	 * <p>
	 * called to release a previously allocated PageContext object. Results in
	 * PageContext.release() being invoked. This method should be invoked prior
	 * to returning from the _jspService() method of a JSP implementation class.
	 * </p>
	 * 
	 * @param pc
	 *            A PageContext previously obtained by getPageContext()
	 */

	public abstract void releasePageContext(PageContext pc);

	/**
	 * <p>
	 * called to get implementation-specific information on the current JSP
	 * engine.
	 * </p>
	 * 
	 * @return a JspEngineInfo object describing the current JSP engine
	 */

	public abstract JspEngineInfo getEngineInfo();

	/**
	 * <p>
	 * Obtain the <code>JspApplicationContext</code> instance that was
	 * associated within the passed <code>ServletContext</code> for this web
	 * application.
	 * </p>
	 * 
	 * @param context
	 *            the current web application's <code>ServletContext</code>
	 * @return <code>JspApplicationContext</code> instance
	 * @since 2.1
	 */
	public abstract JspApplicationContext getJspApplicationContext(
			ServletContext context);
}
